The present invention relates generally to high throughput wireless networks and in particular to aggregation technology.
The next generation of high throughput (HT) wireless networks, to be covered by the 802.11n specification that is currently being formed, specifies 100 Mbps at the MAC SAP (Media Access Control Service Access Port) of an 802.11n device. Frame aggregation is a key technology employed to achieve such a high throughput.
One frame aggregation technique, MRMRA (multi-receiver multi-response aggregation), allows for frames for a number of receivers to be aggregated and allows for immediate responses from those multiple receivers as well, thus greatly increases the MAC efficiency, especially for QoS sensitive enterprise applications, such as wireless voice over IP (WVoIP). A benefit of MRMRA is that MRMRA not only allows for more than double the number of admissible phone calls, but also provides considerable amount of additional bandwidth for regular data traffic.
Another aggregation technique, MMRA (multi-rate multi-receiver aggregation), allows frames for multiple receivers of various rates and modulation schemes to be aggregated. MMRA consists of a bursting of a series of Physical Layer Service Data Units (PSDUs) possibly with various rates and modulation schemes. Each PSDU consists of a single frame or an aggregation of multiple frames either to the same receiver or to multiple receivers of the same rate. MMRA has the advantage of aggregating frames for receivers in a wide range of distances. However, MMRA's lack of support for immediate responses makes its use very limited, especially for latency sensitive applications such as WVoIP.
MMRA does not support multiple responses mainly for two reasons. First, an initiator for an MMRA does not know, in general, how long the bursting will last, so it lacks adequate information to schedule multiple responses. Second, the MMRA approach lacks a protection mechanism to protect the multi-responses from legacy nodes or hidden nodes. Moreover, scheduling multiple responses after the end of bursting is not favorable because it introduces excessive latency into the responses, which can be intolerable for latency sensitive applications, such as WVoIP in an enterprise environment, making QoS requirements hard to meet.
All terms and acronyms unless otherwise defined herein should if defined in the Institute of Electrical and Electronics Engineer's (IEEE) TGn Sync Proposal Technical Specification, TGn Sync Technical Proposal ROO (TGn Sync) dated Aug. 13, 2004, available at http://www.tgnsync.org/techdocs/tgnsync-proposal-technical-specification.pdf, be accorded the definition given in TGn Sync, otherwise they should be given their usual and customary definitions.